Apparatus for catalytic conversion of hydrocarbon vapors



Sept. 7, 1948.

C. S. REED ET AL APPARATUS FOR CATALYTIC CONVERSION OF HYDROCARBON VAPORS Filed Jan. 29-, 1941 INVENTORS Patented Sept. 7, 1948 APPARATUS FOR CATALYTIC CONVERSION OF HYDROCARBON VAPORS Carl S. Reed, New York, and August Henry Schutte, Tuckahoe, N. Y., asslgnors to The Lummus Company, New York, N. Y., a corporation of Delaware Application January 29, 1941, Serial No. 378,486

This invention relates to improvements in processes for effecting chemical reactions by catalysis.

In the field of hydrocarbon conversion by catalysis, it has been customary to use a catalyst in lump or similar form positioned in a suitable reaction chamber. As vapors are passed over the catalyst for reaction, the catalyst rapidly becomes fouled and is rendered inefiicient. It is usually necessary to take the chamber off stream after a relatively short period to revive the catalyst by removing the carbon and other materials deposited thereon during the conversion reaction. Ordinarily several duplicate catalyst chambers are provided for continuous conversion of vapors; but each chamber has only a limited "on stream" period during which it is active, after which time the reactivation must take place. As the catalytic conversion is usually endothermic and the reactivation exothermic,

4 Claims. (C1. 23- -288) temperature conditions in a particular chamber can not be kept stable, and the great heat loss which takes place or the expensive heat recovery systems necessitated as well as the multiplicity of chambers required for continuous operation have made the use, of this process very costly.

The principal object of our invention is to provide a closed cycle catalytic reaction system in which a powdered catalyst is continuously passed through a reaction zone in intimate suspension in the vapors to be reacted and then, after separation from the vaporous reactants, continuously passed through a reactivation zone and thence recycled for admixture with further feed, each zone being continuously maintained at its optimum temperature and pressure conditions whereby the initial cost as well as the operating cost of the catalytic reaction may be reduced.

A more specific object of our invention is to provide an improved control for a continuous powdered catalyst reaction cycle in which the pressures in the various parts of the system are independently maintained'by sufficient heads of powdered catalyst to prevent contamination of vapors or loss of reacted products without requiring complicated and expensive mechanical seals or valves.

Further objects and advantages of the invention will be apparent from the following description of a preferred form of embodiment thereof taken in connection with the attached drawing, which is a diagrammatic view of a suitable flow sheet.

In accordance with our invention, we provide a complete closed continuous cycle process for effecting a catalytic reaction with a powdered catalyst and thereafter reactivating the catalyst and then returning it to be admixed with fresh feed. Such process has primary value and importance in the conversion of hydrocarbons and will be specifically described in connection therewith although it will be appreciated that the process can be used equally as well with other reactants.

More specifically, fresh feed to be reacted, vapors which have been previously heated in some manner, is introduced at to under pressure of blower I2 and under control of damper or valve l3 and is discharged into the conversion zone ll. At the same time, a suitable powdered catalyst is fed into the conversion zone at a predetermined rate by the conveyor it, which may have a suitable feeding means 11.

The conversion zone It may be of any desired and satisfactory type but is preferably an elongated tube of such length and diameter as to assure a sufficient time of reaction during the passage therethrough of the catalyst and vaporous reactants. Such zone may be externally heated, if found desirable, and should be sufficiently insulated such that the temperature drop of the relatively hot vapors and catalyst will not be objectionable during their passage therethrough.

The catalyst is preferably in a powdered form and may be ground as fine as 100-400 mesh, in which condition its area of contact is far greater per pound of catalyst than in the usual lump form. In such form, it will commingle very well with the vapors and will assist in establishing a high conversion within a short time or travel.

After removal from the conversion zone, the reacted vapors and catalyst are separated by the separator l8, which may be of the "cyclone" type. The reacted vapors are withdrawn overhead from the separator as by conduit 20, and the separated catalyst is removed through the vertical conduit 22. Conduit 22 is connected to conduit 24, through which the catalyst is passed by means of a feed means 25 under control of motor 28.

The conduit 22 is relatively long and of such size that, if it is kept full of catalyst, there is no likelihood of any vapor loss therethrough. A powdered catalyst will settle to such an extent that it is possible to have a column of catalyst within reasonable limits of length which will have a pressure drop for small flows of vapor that will be substantially equal to the desired differential of pressure between the separator ll and the lower end of conduit 22. The motor 24, which removes the catalyst from the conduit 2-2, is operated at such a speed that the conduit 22 will be kept full of catalyst. A level control diagrammatically shown at 23 may be used for this purpose.

The catalyst which has been used in the foregoing reaction is now passed from conduit 24 into the reactivation chamber 30 together with air and flue gas from line 3|, which air serves to burn oi! the carbon and other catalyst-fouling contaminants. This reactivation is usually an exothermic reaction, and the chamber 30 may be suitably lined with refractory brick 32 to reduce heat loss to a minimum. Such practice assures removal of the powdered catalyst and the products of combustion, which comprise flue ing a portion oi'the vapors from line 20 through line 63 and line 62 to the fresh feed vapor line H).

material which is recirculated past separator 50..

' A heater 64 may be provided to control the heat conduit 83 into the flue gas separator and heat exchanger 34.

Like separator l8, separator 34 may also be of the cyclone" type and has a similar function in that it separates the reactivated catalyst from the vapors. The vapors (which are the products of combustion) are withdrawn through line 66, and the catalyst settles in vertical conduit 36 which is of sufficient length so that the vapors can not escape through the body of catalyst contained therein. Conduit 33 is provided with a secondary conduit or jacket 31 forming a liquid chamber 39, through which a heat exchanging medium such as water can be circulated; since the catalyst is very hot, substantial amounts of steam can be produced.

If desired, the water chamber 39 may be interconnected by the line 42 with the boiler 43, from which steam may be removed at 44. The boiler 43 is preferably provided with the downcomer 46, which is interconnected with the lower portion of the water chamber 39 by the line 4 l. Provision is made for the introduction of make-up water through the line 46.

The catalyst is maintained at the desired height in the conduit 36 so that a loss of vapor through a the conduit 36 is prevented. As in the former case, this object may be accomplished by means of a level control 48, which controls motor 49, which in turn operates the initial feed means i'l. It will also be noted that the heat transfer from the extended column of hot catalyst is sufficiently great to produce a substantial quantity of steam which can be used for power purposes. The steam in turn tends to maintain a uniform temperature in conduit 36.

It will be thus seen that the system is pressure tight by virtue of the two vertical columns of catalyst which completely isolate the conversion zone and the reactivation zone from each other. Furthermore, the catalyst moves continuously first through an endothermic conversion zone and then an exothermic reactivation zone, each of which may be maintained at its optimum temperature and pressure. If it is desired to alter the flow of catalyst, this may be readily accomplished by varying the speed of either or both motors or by means of a variable speed drive placed between one motor and its driven feed means. Fresh catalyst may be introduced at i9 and is preferably passed through a similar vertical column to automatically provide a pressure seal.

A' part or the vapors removed from the separator i8 after passage through the conversion zone I4 is usually recirculated, the recycle ratio being dependent upon the rate of conversion.

This recirculation may be accomplished by passcontent of the recirculated vapors. Their quantity and quality may be accurately controlled by regulation of the speed of the respective motors 28 and 43 heretofore mentioned and by control of the temperature inconversion zone l4 and heater 54 and also by control of the temperature of the reactivation system, Highly accurate production control is thus obtainable at all times.

In a similar manner, a more complete separation of catalyst from the flue gases or products of combustion may be accomplished by passing the gases in line 60 to the secondary flue gas separator 62,from which the catalyst-free flue gas is withdrawn through line 63 by blower 64 under control of damper 65.

The small amount of catalyst which may be separated out of the flue gases in this secondary separation may be returned to the reactivation zone through line 61. At the same time, some of the flue gas is conducted through line 68, under control of damper l0 and by means of blower ii, into line 3|, into which air is forced from supply line 12 by blower 14. A damper or valve 15 controls the amount of air supplied.

It will be appreciated that some admixture of flue gas with the air is usually desirable to control the exothermic reaction in chamber 30 as the introduction of pure air may cause too rapid a generation of heat therein. Dampers 10 and 15 afford means for accurate adjustment.

It will be appreciated that one of the most important features of the invention is the continuity of flow of all materials, which continuity makes possible the establishment of relatively constant temperature conditions in the respective zones in which the reactions are carried out. While in one zone it may be necessary to continuously add heat, it is possible in the other zone to continuously and simultaneously remove heat which can be applied to useful purposes so that the heat balance will show a minimum fluctuation of heat transfer and a minimum heat loss. I

A second important feature is the flexibility of the apparatus in that, although difierent reaction zones are isolated solely by the natural compactness of the catalyst, it is possible to increase or decrease the rate of flow of catalyst without destroying the effective height of catalyst in the column scT'that no mechanical seals are necessary to establish the relatively diiferent ressuretight zones. Furthermore, it is' possible to obtain a difierential of pressure either at low or high absolute pressures so that the apparatus is useful for various catalytic reactions including the conversion of hydrocarbons.

A third feature is the simplicity of obtaining a substantial separation of the gaseous from the granular materials without great heat loss and the recirculation of the small portions of the catalyst incompletely removed in the first separation stage without deleterious result. The system is inexpensive and simple and has the mini ing a conversion chamber and a catalyst-reactivation chamber, and a closed cyclic catalyst path therebetween including a vertical conduit, means for passing catalyst from one of said chambers to the upper end of said conduit, means for discharging the catalyst from the lower end of said tain the required pressure diiierential by sealing efiect of the compacted material and said conveyor being in constantly open receiving communication with the conduit and being constructed and arranged to free the material received from the conduit from the pressure of said column, and means responsive to fluctuations in height of said packed mass column and operable to control operation of said conveyorto thereby control said discharge for retention of a head of :said material within the conduit sufilcient to conduit to the other of said chambers, said conduit being constructed to form a column of the received catalyst for compacting of the latter by gravity to maintain a required pressure differential between said chambers by sealing efiect oi the compacted catalyst, and a level control device responsive to fluctuations in the level of the catalyst in the conduit to control said discharge of: the. catalyst from the conduit for retention of a head of catalyst suflicient for maintaining said pressure diiferential.

2. In a catalytic conversion apparatus including a conversion chamber and a catalyst-reactivation chamber, closed confined conduits permitting a uniform cycle of movement of catalyst between the chambers and including a vertical conduit, means for passing a catalyst from one of said chambers to the upper end of said conduit, a power driven conveyor operable for discharging the catalyst from the lower end of said conduit to the other of said chambers, said conduit being constructed to form a column of the received cata-. lyst for compacting of the latter by gravity to maintain a required pressure difierential between said chambers by sealing eiTect of the compacted catalyst, and means responsive to fluctuations in the level of the catalyst-in said conduit to control the operation of said conveyor and thereby control said discharge tor retention of a head of catalyst suflicient for maintaining said pressure diiferential.

3. In an apparatus for performing a vapor phase. contact process and including means defining a zone for contact therein of vapor with a solid contact material in a finely divided-state, a closed connection for passing said material between said zone and another zone and maintaining a required pressure diflerential between said zones, comprising a vertical conduit, delivery means for passing said material in suspension within a gaseous medium from one of said zones to the upper end of said conduit, means at the juncture of said delivery means and said conduit to'separate the contact material from the gaseou's,mediu.m for gravitation of the separated contact material freely into the conduit, means to conduct the separated gaseous medium from the upper endv of said conduit, 9. power-driven conveyor operable for discharge of said material irom the lower end of said conduit to the other or said zones, said conduit being constructed and arranged to form a packed mass column of the received material for compacting of the latter by gravity to main-- maintain said pressure differential.

4. In an apparatus for performing a vapor phase contact process andincluding means defining a zone for contact therein of vapor with a solid contact material in a 'finely divided state,

and means defining a zone for reactivation therein of said contact material, a closed connection for conduit of each of said connections being constructed and arranged to form a packed mass column of the received material for compacting of the latter by gravity to maintain a superatmospheric pressure differential between said zones by sealing effect of the compacted material and each of said conveyors being in constantly open receiving communication with its respective conduit and being constructed and arranged to free the material received from the conduit from the pressure of the column, and means responsive to fluctuations in height of said packed mass column and operable to control the operation of the discharge conveyors of the conduits of said connections individually to thereby control the discharge from each conduit for retention of a head oi the material within the conduit 'sufllcient for main tainingsaid pressure difierential.

- CARL S. REED.

AUGUST HENRY SCHUT'I'E.

REFERENCES cn'nn ,The following references are of record in the file of this patent;

UNITED STATES PATENTS Number 4 Name Date 2,224,014 Dunham et al. Dec. 3, 19.40 2,231,231 Subkow Feb. 11, 1941 2,231,424 Huppke Feb. 11, 1941 2,253,486 Belchetz Aug. 19 1941 2,273,075 Weems -1 Feb. 17, 1942 2,302,209 Goddin, Jr, Nov; 17, 1942 2,304,827 Jewell Dec. 15, 1942 FOREIGN PA'I'ENTS Number Country Date 533,037 Germany Sept. 8, 1931 

